The invention relates to a sealing ring, including a support ring made of an impact-resistant material, and a lip ring made of PTFE, where the lip ring has a holding segment and a sealing segment, and where the holding segment is connected with the support ring by an intermediate layer made of a polymer material.
Such a sealing ring is known from German Patent 33 09 538 C2. The sealing ring is intended for rotating shafts or for rods that move back and forth, where the holding segment and the sealing segment of the lip ring are made of the same material. The entire lip ring is made of the same PTFE material.
The invention is directed to further development of sealing ring of the type noted above, in such a way that its manufacture is simplified, and the sealing ring demonstrates better properties in use, for a longer period of use.
To accomplish the task, it is provided that the holding segment and the sealing segment are made of two different PTFE compounds, each adapted to their purpose of use. Preferably, the holding segment is made of PTFE and/or fluorothermoplastics, such as PFA or FEP, and the sealing segment is made of PTFE or a PTFE compound. The material for the holding segment is aimed at the static conditions, and guarantees a good and durable bond with the polymer intermediate layer. The bond can be produced, for example, by gluing the holding segment and the intermediate layer together.
According to another embodiment, it is possible to mold the lip ring onto the intermediate layer during vulcanization of the polymer, under pressure and heat, in the molding die. A durable bond between the holding segment and the vulcanized intermediate layer results from mechanical-thermal bonding.
The holding segment can be clamped between a radial shank and an angled ring.
The sealing segment performs tasks that are completely different from those of the holding segment. In contrast to creating the most durable bond possible between the holding segment and the support ring, the sealing segment must ensure a perfect seal for the medium to be sealed in/out, over a long period of use. If the sealing segment is made of PTFE or a PTFE compound, it will demonstrate both a high level of temperature resistance and a high level of media resistance, with little friction. In addition, the sealing segment is very elastic in the radial direction, in order to follow deviations in concentricity and center offset of the shaft to be sealed, without lifting up from the surface to be sealed. Even under such extreme conditions, leakage is reliably prevented.
In addition, the sealing segment demonstrates a high level of wear resistance. In general, the advantage of a PTFE sealing ring made of two different materials for the holding segment and the sealing segment is that each material can be optimally adapted to its purpose of use, but nevertheless, the holding segment and the sealing segment are formed in one piece, one making a transition into the other.
To seal rotating shafts, the lip ring is arched forward axially in the direction of the space to be sealed, radially on the inside, and surrounds the shaft to be sealed with its sealing region, forming a seal.
The intermediate layer, at a thickness of at least 0.5 mm, can have a Shore A hardness of 65 to 85, preferably 70 to 80, where the ratio between the expanse of the intermediate layer in the radial direction and the related thickness is 3 to 10. Preferably, the intermediate layer has a thickness from 0.7 to 3 mm.
By structuring the intermediate layer in this way, the lip ring is able to follow radial movements of the component to be sealed, without being damaged or coming loose from the intermediate layer.